User:Kesta/LightingWeathersPostProcessing

This page aim to provide an extensive explanation on what lighting and weathers mods are, how they affects the visuals of the game, and what compatibility issues they can produce.

Cells and Worldspaces

There is two different kind of "environment" in Skyrim. Cells, and Worldspaces. A cell is an interior place, while a worldspace is an exterior. There is a few exceptions, where interiors are actually worldpsaces surrounded by walls and ceiling.

There is many differences :

• Only worldspaces have LOD, and use the Grid-based loading system,
• Only worldpsaces have an actual ground. The floor in cells is simply a static meshe.
• Worldpsaces use weathers where Cells use Lighting Templates.

The last point is the one of interest in this page.

The also have many in common :

• They're "containers" for a lot of references, all of the forms found in this area.
• They're navmeshed (or should be).

Lightbulbs

Ligthtbulbs are invisible objects casting lights in a cell or a worldspace. They have several parameters, such as their radius, color, intensity, flickering parameters (to simulate the irregular lighting of a crackling fire for instance), and whether or not they cast shadows.

Lightbulbs mods aim to provide a realistic lighting by moving/deleting/adding/adjusting lightbulbs and lightsources in the Cell.

Here is a view from the Creation Kit to better illustrate the purpose of such mod :

As you can see, the lightbulb (represented by an ampoule) isn't located exactly where the light should originate (the brasero). This lead to inconsistent lighting. Lightbulbs mods move this kind of lightbulbs to a more consistent location.

Additionally, there is many lightbulbs that doesn't have any designated lightsource, leading to area being lit by nothing but an invisible source. Lightbulbs mods usually delete those lightsbulbs, or add an actual object that would cast such light. They may also add lightbulbs where there isn't any, but an object that would cast light is present (that's the case of many candles in vanilla).

Additionally, lightbulbs mods aim to provide a workaround about two engine limitations present in Skyrim :

• A mesh partition can only be lit by 3 lightbulbs at max. If 4 lights try to lit the same mesh partition, this partition will flicker.
• Only 4 shadow-casting lights can be visualized at the same time. If more shadow-casting lights are present, one of them will be completely disabled.

In order to prevent the mesh-partition issue, advanced lightbulb mods provide new meshes, more partitioned than the vanilla ones. Here is an illustrated example from ELFX :

As you can see, the huge partition from the 1st screen (vanilla), including the floor, the stair, and the part under the door, have been splitted into several small partitions. Only one of those sub-partitions is selected is selected in the second screen (elfx). The original big partitions is now splitted into several smaller ones, preventing the flickering that would be caused by 3 lightbulbs in the 1st floor (lighting the staircase), and 3 other lighting the 2nd floor (lighting the floor).

Some lightbulbs mods example : Enhanced Light and FX (only cover lightbulbs in interior) Enhanced Light and FX - Exteriors (only cover lightbulbs in exteriors) Relighting Skyrim Realistic Lighting Overhaul

Lighting

This section is about interior cells only.

The whole lighting scene isn't only dependant of the lightbulbs in an interior cell. Several parameters are directly dependent on the cell itself.

Lighting Template/Properties

Lighting is handled by several properties. Most of those are first set with a lighting template, and eventually tweaked manually by the modder on a per-case basis to achieve the final effect. There is 3 sub-families of lighting :

• Ambiant Lighting : Set the ambiant light color.
• Directional Lighting : Set the color that will be reflected on FX such as fog/myst.
• Fog Lighting : Set the color of the fog, this greatly impact the feeling of the scene.

Interior Fog

Interior fog have more properties than just its color. Especially its distance. A "close" fog will lead to reduced visibility, possibly preventing the player to see the end of a room/corridor he is in, while a very far fog will let him see very far.

Imagespace

An imagespace is an in-engine post-processing template used to further tweaks the visuals. This handle bloom, depth of field, sharpening, saturation, etc...

Here are two examples from the Creation Kit wiki to see how image space can affect the visual of a cell : File:250px-AzurasStarImageSpace.jpgFile:250px-FrostmereCryptImageSpace.jpg

Imagespace and Lighting Templates/Properties are designed to work together. For consistent visuals, you should not use the light properties of a mod, and the imagespace from another.

Fake Exterior lighting

Cells can be marked "Use Exterior Lighting", and then assigned to a weather. This is used in cells that have see-through ceiling, allowing to see the clouds from the outside weather, and benefit from day/night lighting variations.

Weather

Weathers are essentially to a worldspace what the lighting is to a cell. It handle the ambiant colors, as well as the color spread by the sun (which can affect the final color of your textures. A redish sun-spread color on a blue-ish snow texture can result into green-ish snow), the color of the sky, eveyrthing related to the exterior fogs, and several layers of clouds (both their texture and their colors).

As for cell lighting, a weather have a dedicated imagespace attached.

Finally, weathers can also have a "precipitation type", such as rain/snow (which is just a flat overlay), or a special visual effect for more advanced rendering (such as Vivid Snow).

This is also important to note how the weather-system work in skyrim. The map is divided into "regions". Here is a map of skyrim with all the regions from vanilla :

Each region have a set of potential weathers. Advanced weather mods (which can be considered as "climate mods") doesn't only modify the feel of the weathers, but directly edit region settings to add/remove weathers from the list, adding to the variety of weather seen accross all of Tamriel. Most known mods to do so are :

• Climates of Tamriel (400 new weathers)
• Vivid Weathers (500 new weathers)
• NLA (18 new weathers)
• Expanded Snow system (8 new weathers, only cover snowy regions).

ImageSpace Modifiers

Imagespace modifiers are similar to imagespaces, but weren't originally thought to be applied permanently. They're meant to modify the imagespace during special events like when casting a spell (like with the Orc's Berserker Rage).

However, some mods use them to adjust the visual feeling of the game, which is in essence "casting a spell that last forever". The most known mod providing such feature is Imaginator.

Imagespace modifiers doesn't directly conflict with anything. They doesn't "override" the current Imagespace, but are applied atop of it. However, they can lead to inconsistent visuals as they apply changes in a generic fashion (increasing the saturation will increase the saturation in any situation, which can wipe out the gloomy feeling intended by a specific mod in a specific weather or area).

Post-processing

Post-processing mods (SweetFX, ReShade, ICBINE, ENBseries) essentially serve the same purpose as an ImageSpace Modifier mod. However, they directly rely on DirectX features instead of the in-engine post-processing, offering high-quality features, and can alter way more things (ENBs can completely revamp the fog, which is impossible to achieve with imagespace modifiers).

The "big question" is "why do ENB Preset authors say their preset is designed for a specific weather/lighting/water mod?"

• Water : This is usually more a recommandation than an actual compatibility issue. ENBs can affect the way the water look, but the differences between water mods are too faint to lead to any weird visual on this side.
• Lighting :
  • Lightbulbs mods have nothing to do with post-processing and all are compatible with any ENB preset, as explained before they only aim to improve te lighting consistency.
  • Lighting mods are indeed affected by post-processing. Though the features available in ENBs for interiors aren't as fleshed-out as they are for weathers, interiors-focused presets are greatly affected by the lighting mod used. A good thing to keep in mind however, is that most ENB Presets available are essentially focused on exteriors and not interiors.
• Weather : ENBseries is able to recognize which weather is currently active, and adjust post-processing in consequence. Advanced/High-quality presets all include weather-specific post-processing, tailored for a specific weather. If the post-processing have been tailored for a bright blue sky with bright white clouds, but the weather mod used change those into a orange-ish sky with pink-colored clouds (yes, this happens. Most weather mod actually use those colors for dusk), the final visual will look weird, at best. A top of that, new weather introduced by the mod won't be recognized at all, which will lead the preset to use a "default" post-processing. Since most of the post-processing is handled on a per-weather basis, most of the preset's features won't show up at all on new weathers.